1. Field of the Invention
This invention relates to press brakes and to workpiece locating or positioning stops or gauges for press brakes and the like.
2. Description of the Prior Art
The U.S. Pat. No. 3,618,349, issued Nov. 9, 1971 to Gerald V. Roch, for a gauging system for presses, discloses a system for operating front and rear gauges in a predetermined sequence automatically. One of the references cited in that patent was U.S. Pat. No. 3,176,556 to Roberts, describing a tape-controlled lead screw drive for the back gauge of a guillotine-type shearing machine. U.S. Pat. No. 3,826,119 issued July 30, 1974, shows a rear gauge driven by a lead screw.
Although there are situations where a rear gauge bar is short enough that a single point of drive for it is suitable, there are many instances when, due to the substantial length of the gauge bar, drive for it must be provided in at least two horizontally spaced points along its length. The above-mentioned Roch patent provides for this by using a pair of horizontally spaced cylinders for driving the rear gauge. U.S. Pat. Nos. 1,366,409 issued Jan. 25, 1921, and 3,115,801 issued Dec. 31, 1963, show rear gauges for metal shearing machines and which employ screw drives at spaced points, the earlier patent showing two handwheels, one for each screw, and the other showing a single handwheel with a cross-shaft for driving the two screws. Rear gauges using twin screw drives with a single motor driving the two screws, one of them by means of a cross-shaft, have been advertised by the organization named "Colly Constructions Hydromechaniques" of Lyon-Villeurbanne, France. Its advertisement said the apparatus could provide for eight successive bends preselected manually by means of eight sets of digital switches.
A press brake rear gauge apparatus having two drive screws and motors has been advertised by the Niagara Machine and Tool Works of Buffalo, N.Y. It was referred to as the "Bend-A-Matic" and was intended to employ digital switches as in the aforementioned Roch patent for preselection of gauge stopping positions, together with an integrated solid state circuit control. It was said to be programmable for three different bend dimensions, each to be established by adjusting certain switches in three sets of digital switches, one set for each of the bend dimensions. There was no provision for alternate operation of front or rear gauges.
There has remained a need for greater versatility in terms of the number of pre-selectable bend dimensions, the facility of switching from front gauge to rear gauge operation and vice versa, convenience of mounting and relocation of gauging apparatus on the press brake, high speeds, low cost, and minimal danger of overloading the gauges themselves or the drives for them.
According to one embodiment of our invention, a basic carriage mounting frame and drive motor are employed for the front gauges and the rear gauges. A microprocessor is employed in a microcomputer to facilitate entry of dimensional data, bend sequence instructions, correction factors, and control operation of drive motors for lead screws driving either a pair of front gauges, or a rear gauge having twin lead screw drive. Although it is known to employ a computer to control relative speeds of feed rolls in papermaking and handling machines, and also to control drive motors at opposite ends of long overhead gantry cranes, we do not know what specific techniques were used in implementing such controls. Integrated circuit logic has also been used for control of independent motors driving equipment at different points but in synchronism in terms of time and direction. Control Systems Research has done considerable work in synchronization control of shafts by phase locking methods.
Cambion has introduced numerical control equipment for point to point movement of workpiece support tables for machine tools, but we do not believe that their literature has ever referred to control of twin parallel synchronized drives or twin lead screws associated with their controllers. They employed stepping motors. It is believed also that twin lead screw drive has been done by C. Behrens of Alfeld, Germany, employing a single motor and some kind of numerical control for clutches to synchronize the drive of the two lead screws with only the one motor. It is described in U.S. Pat. No. 3,650,133. Further details are unknown to us. We are unaware of any use heretofore of a microcomputer or microprocessor in the control of two parallel drives for a single item.